Skipper impoverishment on large West Mediterranean islands (Lepidoptera Hesperioidea): deterministic,historical and stochastic factors

Biogeographical analyses are applied to skipper (Hesperioidea) presence/absence data from the Western Mediterranean mainland and the three largest islands (Sardinia, Corsica and Sicily) in order to identify potential conservation issues. The analyses performed on species, both collectively and individually, indicate that regional species richness and occurrence in the Mediterranean zone are largely predicted by latitude and area but that islands have impoverished faunas. Several species, predicted to be present on these islands from logistic regression of their continental distributions, are actually absent. The number of species predicted to be present from logistic regression analyses for each island, closely matched the number of species predicted to occur in regional-focused multiple regression analysis. This suggests that missing species have been identified. When compared with species that occur in Sicily and Corsica, the missing species are shown to differ for ecological traits, mainly those linked to altitudinal tolerance. No ecological distinctions were disclosed for Sardinian skippers suggesting a mainly stochastic colonisation. These results, and those from an analogous study carried out on Papilionoidea, point to Hesperioidea having (i) overall more impoverished faunas on islands and (ii) being subject to stochastic or historical colonisation events more than Papilionoidea. Species not predicted to occur on islands based on their mainland distributions and ecological traits, are foci for conservation attention. However, as many species becoming extinct on the islands may be irreplaceable, all species, in particular the Sardinian ones, deserve to be conserved.     

A novel mechanism of action of corticotropin releasing factor in rat Leydig cells

We have recently demonstrated the presence in the rat Leydig cells of a corticotropin releasing factor (CRF) receptor and an inhibitory action of the peptide on human chorionic gonadotropin (hCG)-induced cAMP generation and steroidogenesis. The inhibitory action of CRF was unaffected by pertussis toxin and was completely reversed by 8-bromo-cAMP (Ulisse, S., Fabbri, A., and Dufau, M. L. (1989) J. Biol. Chem. 264, 2156-2163). In this study, we have evaluated the participation of protein kinase C in CRF action in the Leydig cells and the level of the gonadotropin signal pathway affected by CRF. Binding of 125I-labeled ovine CRF to Leydig cell membranes was reduced by GTP and guanyl-5'-yl imidodiphosphate (Gpp(NH)p), in a dose-dependent manner. Phorbol 12-myristate 13-acetate, like CRF, caused time-dependent inhibition of hCG-induced cAMP generation and steroidogenesis. This inhibitory action was reversed by 8-bromo-cAMP. Both CRF and 12-O-tetradecanoylphorbol-13-acetate did not affect 125I-hCG binding. No additive effects of CRF and the phorbol ester were observed in these studies. CRF caused a rapid translocation of protein kinase C in Leydig cells. Preincubation of cells with protein kinase C inhibitors or TPA-induced depletion of protein kinase C prevented the inhibitory actions of CRF and TPA. CRF and TPA were able to inhibit the stimulation of cAMP and testosterone production by cholera toxin and forskolin. Adenylate cyclase stimulation by Gpp(NH)p, luteinizing hormone + Gpp(NH)p, and NaF in crude membranes or by forskolin and manganese in solubilized membranes, prepared from CRF- and TPA-treated cells, was also markedly inhibited. We conclude that CRF receptors interact with a pertussis toxin-insensitive G protein (possibly Gp) in the Leydig cell and that the inhibitory action of CRF on Leydig cell function is exerted mainly on the catalytic subunit of adenylate cyclase through a direct or indirect action of protein kinase C.     

Effect of potassium humate on apple cv. ‘Golden Delicious’ cultured in vitro

The effects of humic substances on in vitro culture of Golden Delicious apple are reported. Potassium humate (KH) when used in proliferation showed a negative interaction with BA while it enhanced rooting when IBA was not present in the culture medium. In the presence of IBA, KH increased root number and reduced root growth. The highest concentration tested, 500 mg l^-1, caused a drastic reduction in root system development. 50 mg l^-1 KH hastened rooting and plants grew more rapidly when transferred to soil.     

Supra-additive stimulation of adenylate cyclase activity by prostaglandin E2 andD-Ala2-met-enkephalinamide in the guinea-pig superior cervical ganglion: Role of Mg2+ ions

Agonists modulation of Mg²⁺-dependent adenylate cyclase activity has been studied in guinea-pig superior cervical ganglion crude membrane preparations. In the absence of receptors ligands, Mg²⁺ stimulates the enzyme in a concentration-dependent manner. The dose-activation curve shows heterogeneity and two components with higher and lower apparent affinity states, are extrapolated. In the presence ofD-Ala²-met-enkephalinamide only one component is present and the apparent affinity of the ganglionic adenylate cyclase system for the divalent cation as well as Vmax are inhibited. On the contrary, prostaglandin E₂ increases affinity and Vmax values of the lower and, to a lesser extent, of the higher Km component. When the two drugs are tested in combination, not only the inhibitory effect of the opiate is overcome, but a large increase of the apparent affinities and Vmax values for both components is obtained, suggesting the involvement of the Mg²⁺-regulated subunits of the adenylate cyclase system in the supra-additive stimulation mechanism of the enzyme.     

Measurement of nutrient spiralling during a period of continuous surface flow in a Mediterranean temporary stream (Arroyo de La Montesina, Spain)

Uptake rate of calcium, potassium, nitrate-N and phosphorus were measured in a second order Mediterranean temporary stream, in February and March 1992. This study analyzed a period of continuous surface flow between two hydrologic disturbance events (flood and drought) of an annual hydrological cycle (1991–92).The lowest values of uptake length were recorded for nitrate-N in February 92 and calcium in March 92. Nitrate had the highest uptake rate in both release performances, and potassium showed the lowest uptake rate values. The increase of calcium and nitrate uptake rate between February 92 and March 92 suggested a higher ecosystem efficiency in nutrient retention with a higher temperature and light intensity and slower water velocity, discharge and water depth. These results obtained were similar to those reported in permanent streams, indicating that in periods of continuous surface flow (without extreme hydrologic disturbance), abiotic factors can influence nutrient retention in temporary streams.     

The Jurassic succession in west-central Argentina: stratal patterns, sequences and paleogeographic evolution

Jurassic rocks in west-central Argentina are predominantly marine and marginal-marine siliciclastics, associated with prominent but volumetrically subordinate carbonates and evaporites. Facies developments were ruled by paleogeographic persistence within the southern-infratropical latitude belt (within 40–50°S) and by siliciclastic derivation from the Patagonian hinterland to the southwest. Minor volcanic and volcaniclastic supply arrived from the west, out of a magmatic belt related to Circum-Pacific convergence. Timing of the main marine-flooding events and general correspondence with the high-rank stratal packaging recorded in western North America, suggest that global eustasy was also a factor in controlling the local stratigraphic record. Early Jurassic sedimentation occurred within a series of semi-isolated depocentres linked to fault-bounded Triassic troughs. The Sinemurian-Toarcian deposits record depocentre expansion and coalescence. These trends were coeval with progressively more widespread marine invasions from the northwest and west, leading to an elongate marine seaway which connected central Patagonia with the Pacific domain. During the Aalenian-Bajocian the region was subject to a more subdued tectonism and the foreland side of the basin became fringed by an extensive clastic embankment. Bathonian and Early Callovian were times when coarse clastics prograded into the basin, while the marine embayment shrank as a result of stepwise forced regressions. During Late Callovian to Oxfordian globally rising sea-level, the depocentre witnessed the appearance of cosmopolitan invertebrates and a stratal pattern of basin widening and depositional underbalance, that promoted cratonward onlap and inception of widespread carbonate deposition. Ooidal-coralline carbonate development was terminated after a relatively sudden (Messinian-style) event that desiccated a large tract of the Andean basin, and favored massive precipitation of anhydrite. In the course of the Kimmeridgian the evaporite basin was largely flooded by siliciclastics and turned into a broad and featureless mudflat-salina complex, linked to a widespread erg and to an ephemeral drainage system. By the Tithonian, at a period of peak oceanic stand, marine connection was reinstated and recorded as the most widespread Jurassic transgression across the Neuquén-Aconcagua embayment. Shelfal deposition consisted of molluscs and ooid-dominated carbonate terraces that grew in pulses tuned to eustatic fluctuations. Like in other prolific petroleum provinces around the world the Tithonian basinal strata involve widespread euxinic deposits featuring unusually high organic content.     

Complete sequence of a new HLA-B35 allele found in a tribe of Mapuche Indians in the south of Argentina

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number U17107. The nameB*3509 was officially assigned by the WHO Nomenclature Committee in December 1994